The present invention relates in general to encoder/decoders, and, more particularly, to an encoder/decoder for an emergency alert system.
The patent to Ganzer et al., U.S. Pat. No. 5,121,430, issued on Jun. 9, 1992, for Storm Alert For Emergencies, discloses an emergency alert system. The emergency alert system includes a code generator which is part of a broadcast transmission system. The code generator produces a composite code signal. One component of the composite code signal designates a geographical area for receiving a message. Another component of the composite code signal designates the alert message for the designated geographical area. The composite code signal is encrypted and the encrypted composite code signal modulates an audio carrier by frequency shift keying. Remote receivers are tuned to the broadcast transmitter. The receivers demodulate the encrypted composite code signal and recovers therefrom the composite signal. A data comparison circuit within the receivers compares the user location code with the designated geographical location code. If a match is detected a selected number of times over a predetermined time period, the receivers in which the match is detected will activate an alarm and the alert message is reproduced by the receiver. The broadcast transmitter may be a television transmitter and the remote receivers may be television receiver circuitry.
In the patent to Permut et al., U.S. Pat. No. 4,155,042, issued on May 15, 1979, for Disaster Alert System, there is disclosed a central alert station. The central alert station includes a code selector and transmits coded radio frequency activation signals specifying the geographical area. The central alert station also transmits audio signals containing an audio message. Simultaneous transmission of the coded activation signal and the audio signal are possible by multiplexing both signals on the same frequency by employing a multiplexer. A plurality of radio frequency receivers are remotely located. The output of each of the radio frequency receivers is supplied to a decoder, which analyzes the coded radio frequency activation signal. Detection of a coded activation signal by the decoder results in the activation of power circuits. Each decoder is coupled to its associated radio frequency receiver and enables user entry of the location code corresponding to the geographical area of the associated receiver. Activation of the power circuits results in the operation of an audible alarm, a display of a visible alarm, reproduction of an audio message, and the activation of desired auxiliary units.
The patent to Giallanza et al., U.S. Pat. No. 4,383,257, issued on May 10, 1983, for Message Communication System With Message Storage, discloses a transmission system. The transmission system developes a binary encoded data train having a header followed by a message. The data train is applied to a carrier frequency to modulate the carrier using frequency shift key techniques. The header uses synchronizing signals, one or more address signals, and a message. One or more receivers receive the message in response to an address signal in the header. The digital data is converted into audio signals for modulating the transmitted signal by frequency modulation. A receiver/demodulator detects the binary encoded data train and demodulates the carrier modulated by the audio frequencies into the corresponding sequence of binary logic levels. The demodulated digital data is then applied to a bit synchronizer that synchronizes the internal clocks of the receiver to the incoming data train so that each of the binary data bits can be sampled and applied to a decoder. The decoder stores the message prior to display of the message on a visual alphanumeric display.
In the patent to Bernard et al., U.S. Pat. No. 4,956,875, issued on Sep. 11, 1990, for Emergency Radio Alerting And Message Transmitting System Directable To Selected Classes And Numbers Of Receivers, there is disclosed an emergency radio alerting and warning system. The emergency radio alerting and warning system includes a frequency modulated transmitter. The broadcast signal from the frequency modulated transmitter uses an encoder to provide a code to enable broadcasting to be made to particular receivers in a selected geographical location. The broadcast signal is a composite signal that also includes sound messages and audible alarms. Frequency modulated receivers are receptive, but inactive, until the specific encoded geographical signal at frequency modulated receivers is received. Upon detecting the specific encoded geographical signal, the activated frequency modulated receivers activate an audible alarm followed by the alert message.
The patent to Rush, No. U.S. Pat. No. 5,030,948, issued on Jul. 9, 1991, for Multiple Characteristic Sensitive Addressing Scheme For A Multiple Receiver Data Network, discloses a data transmission network. The data transmission network includes a transmitter for transmitting messages via a radio wave type communications medium, such as a sub-audible carrier or a frequency modulated broadcast band or an ultra high frequency television spectrum for incorporation into existing television transmission. The data transmission is a composite signal that includes a code component and a message component. Receivers compare the code component. Should the code of the receiver match the transmitted code, then the message is stored. The stored message may be outputted by alternative apparatus including a circuit capable of generating audio from digital data.
In an article circulated on Apr. 18, 1993, by Frederick M. Baumgartner of TFT, Inc. of Santa Clara, Calif., at an NAB Convention in Las Vegas, Nev., there is disclosed an emergency broadcast system in which a microprocessor scans audio and data sources for emergency information. The emergency broadcast system employs a header containing location and emergency alert information. The emergency alert information is decoded by a receiver system that scans between several information sources. Decoders scan or monitor looking for the emergency information source preamble and data. Decoders decode the original emergency information source header, data and end of message and then regenerate the frequency shift keying of the emergency information system signal. The sources of emergency information, which provide audio signal input are connected to an audio bus. A voice storage is provided for review or rebroadcast of emergency information. The emergency information system utilizes all electronic media, including broadcast television, radio, cable delivered services, satellite services, data services, and government and private warning services.